Designation C693 − 93 (Reapproved 2013) Standard Test Method for Density of Glass by Buoyancy1 This standard is issued under the fixed designation C693; the number immediately following the designatio[.]
Trang 1Designation: C693−93 (Reapproved 2013)
Standard Test Method for
This standard is issued under the fixed designation C693; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1 Scope
1.1 This test method covers the determination of the density
of glasses at or near 25°C, by buoyancy
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use It is the
responsibility of the user of this standard to establish
appro-priate safety and health practices and determine the
applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 ASTM Standards:
E12Terminology Relating to Density and Specific Gravity
of Solids, Liquids, and Gases(Withdrawn 1996)2
3 Terminology
3.1 Definitions:
3.1.1 density of solids—the mass of a unit volume of a
material at a specified temperature The units shall be stated as
grams per cubic centimetre (see TerminologyE12)
4 Significance and Use
4.1 Density as a fundamental property of glass has basic
significance It is useful in the physical description of the glass
and as essential data for research, development, engineering,
and production
5 Apparatus
5.1 Analytical Balance, with sensitivity and accuracy of 0.1
mg
5.2 Beaker, of convenient capacity (250 to 750 cm3) to fit
inside the balance chamber and allow immersion of the basket
or wire loop specimen holder in distilled water
5.3 Thermometers, calibrated (20 to 30°C), sensitive to
0.1°C for determining air and water temperatures
5.4 Nickel-Chromium-Iron or Platinum-Alloy Wire, less
than 0.2-mm diameter for suspending the specimen either in a basket or a loop made of the same wire The suspension wire shall be cleaned by degreasing or heating in a vacuum.3An acceptable alternative method of cleaning the platinum-alloy wire is to heat in an oxidizing gas flame until there is no longer any color emitted from the gases passing around the wire
5.5 Weights, with accuracy of 0.1 mg.
5.6 Barometer, with sensitivity of 1-mm Hg (optional, see
Note 3)
6 Reagent
6.1 Distilled Water, fresh, boiled, and used within 24 h,
allowed to stabilize at balance air temperature for at least 2 h
in the beaker
7 Test Specimen
7.1 Specimens weighing about 20 g, with a minimum of seeds or other inclusions (Note 1), shall be taken or cut from the sample object, preferably in cylindrical or rectangular bar form with smooth, slightly rounded surfaces having no cracks
or sharp edges
N OTE 1—For a specimen of 20 g with a density of approximately 2.5 g/cm 3 , a gaseous void of diameter 2 mm will cause an error in measured density of 0.05 %.
7.2 The specimens shall be cleaned, handling them with tweezers throughout subsequent operations, by immersion preferably in an ultrasonic bath of hot nitric acid, chromic-sulfuric acid, or organic degreasing solvent, followed by a rinsing in alcohol and distilled water For samples only soiled
by ordinary handling or exposure, adequate cleaning may be obtained using a warm 2 % volume MICRO-brand4detergent, followed by a deionized or distilled water rinse
8 Procedure
8.1 Hold the specimens and covered beaker of boiled distilled water near the laboratory balance until the water has cooled to ambient temperature before weighing
1 This test method is under the jurisdiction of ASTM Committee C14 on Glass
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
Physical and Mechanical Properties.
Current edition approved Oct 1, 2013 Published October 2013 Originally
approved in 1971 Last previous edition approved in 2008 as C693 – 93 (2008).
DOI: 10.1520/C0693-93R13.
2 The last approved version of this historical standard is referenced on
www.astm.org.
3 Bowman, H A., and Schoonover, R M., “Procedure for High Precision Density
Determinations by Hydrostatic Weighing.” Journal of Research, National Bureau of
Standards, Vol 71C, No 3, July–August 1967, pp 179–198.
4 Manufactured by International Products Corporation, PO Box 70, Burlington,
NJ 08016.
Trang 28.2 Read the laboratory air temperature to the nearest 1°C.
Read the barometric pressure to the nearest 1-mm Hg A fixed
laboratory average barometric pressure estimate is an
accept-able alternative to the barometric pressure measurement (see
Note 3) Determine the density, ρA, of the air from Table 1
8.3 Weigh the glass specimen in air to the nearest 0.1 mg
and record as W A
8.4 Place the beaker of water with immersed thermometer
on a platform supporting it over the balance pan so that the pan
or balance arm is free to swing
8.5 Place the specimen in the basket or loop holder and hang
this holder from the balance arm by means of a suitable hook
and the suspension wire Immerse the basket and specimen by
raising the beaker of distilled water until the surface of the
water is at a predetermined reference position on the
suspen-sion wire
N OTE 2—Before use, the beaker of water should be covered to minimize
dust Just before the weighing of the basket and specimen, the water
surface near the suspension wire may be cleaned by a vacuum nozzle or
pipet technique The suspended assembly should be agitated slightly with
a vertical motion to wet the suspension wire above the meniscus at the
reference position and to ensure that no air bubbles are adhering to the
glass or holder.
N OTE 3—A laboratory average barometric pressure estimate may be
determined from the elevation of the laboratory estimated to the nearest
170 m (500 ft) The national average barometric pressure corrected to sea
level (0 elevation) is 760-mm Hg For each 341-m (1000-ft) increase in
elevation, barometric pressure decreases by approximately 25-Hg For
glass densities in the range of 2 to 6 g/cm 3 , a barometric pressure estimate
based on this relationship will result in density measurement bias of less
than 0.004 % under normal atmospheric pressure variations.
8.6 Weigh the glass and holder in the distilled water to the
nearest 0.1 mg and record as W T
8.7 Remove the glass from the holder At the reference
position, weigh the empty holder in the distilled water, to the
nearest 0.1 mg and record as W O
8.8 Read the distilled water temperature to the nearest 0.1°C
and determine the water density from Table 2 Record this as
ρW
9 Calculation
9.1 Calculate the weight of the specimen in water, W W, as
follows:
9.2 Calculate the glass density, ρ, at the average air-water
laboratory temperature, T L, as follows:
ρ 5~W AρW 2 W WρA!
9.3 Calculate the glass density, ρS, at a standard reference
temperature, T S, as follows:
ρS5 ρ 113α~T S 2 T L! (3) where α is the approximate instantaneous coefficient of
linear thermal expansion at T S
N OTE 4—For low expansion glasses or small temperature intervals or both, this correction is not required.
10 Report
10.1 Report the following information:
10.1.1 Identification of test sample, production, manufacturer, glass type, and so forth as required,
10.1.2 Density of glass, ρ or ρ S, in grams per cubic centimetre,
10.1.3 Temperature, T S or T L, for which glass density is reported,
10.1.4 Thermal history of specimen If unknown, it should
be so stated, and 10.1.5 Estimate of the volume of voids and inclusions
11 Precision and Bias
11.1 Precision:
11.1.1 With proper precautions taken to minimize dissolved air in the water and adhering air bubbles during immersion of the specimen and holder, this procedure will yield glass density
to a standard deviation within 60.1 %
11.1.2 With precautions taken to minimize air-water tem-perature differences and to correct for temtem-perature, etc., effects
on air and water density, this procedure will yield glass density
to a standard deviation close to 60.03 %
11.2 Bias—Three glass density standard reference materials
are available from the Standard Reference Materials Program, National Institute of Standards and Technology Bias can be experimentally assessed by measurement of density by this procedure for these glasses
TABLE 1 Density of Dry Air, g/cm 3
Temperature,
°C
Pressure, mm Hg
20 0.001 141 0.001 157 0.001 173 0.001 189 0.001 205 0.001 221
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TABLE 2 Density of Air-Free Water, g/cm 3
Temperature,